Improve configuration documentation

## Edit existing content 📝

### Pages to modify
- /usage/configuration
- /usage/configuration/credentials
- /usage/configuration/import-export-configuration
- /usage/configuration/network

### Required changes

Improve Infection Monkey's documentation for configuration. Here are some recommendations:

- Move the `credentials` page under `features` and give it an appropriate name.
- Transform the relevant parts of import/export configuration page into a **How To**.
- Transform the relevant parts of import/export configuration page into **Explanation** under `features`.
- Transform the `network` page into an appropriate **Explanation**. Perhaps this should be part of the [Agent Propagation **Explanation**](https://github.com/guardicore/monkey/issues/4215).
- Add a complete reference for the configuration (see #4210 for some information on how to do this).
- Document any other `features` of interest using the appropriate type of documentation according to [Diátaxis](https://diataxis.fr/).